title: RNA-Seq analysis of Citrus reticulata in the early stages of Xylella fastidiosa infection reveals auxin-related genes as a defense response.
abstract: BACKGROUND
  Citrus variegated chlorosis (CVC), caused by Xylella fastidiosa, is one the most important citrus diseases, and affects all varieties of sweet orange (Citrus sinensis L. Osb). On the other hand, among the Citrus genus there are different sources of resistance against X. fastidiosa. For these species identifying these defense genes could be an important step towards obtaining sweet orange resistant varieties through breeding or genetic engineering. To assess these genes we made use of mandarin (C. reticulata Blanco) that is known to be resistant to CVC and shares agronomical characteristics with sweet orange. Thus, we investigated the gene expression in Ponkan mandarin at one day after infection with X. fastidiosa, using RNA-seq. A set of genes considered key elements in the resistance was used to confirm its regulation in mandarin compared with the susceptible sweet orange.
  
  
  RESULTS
  Gene expression analysis of mock inoculated and infected tissues of Ponkan mandarin identified 667 transcripts repressed and 724 significantly induced in the later. Among the induced transcripts, we identified genes encoding proteins similar to Pattern Recognition Receptors. Furthermore, many genes involved in secondary metabolism, biosynthesis and cell wall modification were upregulated as well as in synthesis of abscisic acid, jasmonic acid and auxin.
  
  
  CONCLUSIONS
  This work demonstrated that the defense response to the perception of bacteria involves cell wall modification and activation of hormone pathways, which probably lead to the induction of other defense-related genes. We also hypothesized the induction of auxin-related genes indicates that resistant plants initially recognize X. fastidiosa as a necrotrophic pathogen.
authors.affiliation: Departamento de Biotecnologia, Centro APTA Citros Sylvio Moreira, CP4, Cordeirópolis, SP 13490-970, Brazil. marcos@centrodecitricultura.br.
authors.forename: Carolina M
authors.initials: CM
authors.lastname: Rodrigues
authors.forename: Alessandra A
authors.initials: AA
authors.lastname: de Souza
authors.forename: Marco A
authors.initials: MA
authors.lastname: Takita
authors.forename: Luciano T
authors.initials: LT
authors.lastname: Kishi
authors.forename: Marcos A
authors.initials: MA
authors.lastname: Machado
mesh_terms: D002473:Cell Wall / Q000187:drug effects / Q000235:genetics; D002957:Citrus / Q000187:drug effects / Q000235:genetics* / Q000276:immunology / Q000382:microbiology*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant / Q000235:genetics; D007210:Indoleacetic Acids / Q000494:pharmacology*; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology*; D057865:Plant Immunity / Q000187:drug effects / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D059748:Proteolysis / Q000187:drug effects; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction; D064210:Secondary Metabolism / Q000187:drug effects / Q000235:genetics; D017423:Sequence Analysis, RNA / Q000379:methods*; D013312:Stress, Physiological / Q000187:drug effects / Q000235:genetics; D025801:Ubiquitin / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics; D044167:Xylella / Q000502:physiology*
chemical_list: D007210:Indoleacetic Acids; D010940:Plant Proteins; D025801:Ubiquitin